1. Field of the Invention
The present invention relates to a method of forming a film in a semiconductor manufacturing process, and more particularly to a method of forming a film of a semiconductor, a conductor, an insulator, etc. in a recess present on a surface of a substrate to be treated by using a vapor phase growth method.
2. Description of the Related Art
There are several methods of forming a film on a surface of a substrate to be processed. One of them is a vapor phase growth method. In the vapor phase growth method, a chemical reaction of material gas at high temperatures is utilized. Although the reaction at high temperatures is disadvantageous, this method is advantageous in that various kinds of films can be obtained with high adhesion strength and the control of film thickness is relatively easy. As an apparatus for actually forming a film on the surface of the substrate to be processed, a batch-type low pressure CVD (LPCVD) apparatus, etc. have been widely used. In the batch-type low pressure CVD apparatus, films are simultaneously formed on surfaces to be processed of a plurality of substrates.
In the field of manufacture of semiconductor devices, however, the diameter of a wafer or a substrate to be processed has recently been increased more and more. In the batch-type LPCVD apparatus, it is, therefore, difficult to keep in-plane uniformity of a film formed on a wafer or uniformity among films formed on wafers. Under the circumstances, in the field of manufacture of semiconductor devices, there is a tendency that a multi-chamber apparatus for forming films on wafers one by one is widely used.
In the multi-chamber apparatus, in order to increase the through-put, it is necessary to increase the film formation rate. If the temperature of the surface to be processed of the wafer, i.e. the film formation temperature, is raised, the film formation rate can be increased. However, if the film formation temperature is raised, there occurs a problem in that a step coverage or burying properties on fine recesses present on the wafer will deteriorate.
In the manufacturing process of semiconductor devices, there are many cases where buried layers are formed in the recesses present on the surface to be processed of the wafer or thin films are formed along inner walls of the recesses. For example, in the manufacturing process of memories, it is necessary to perform a step of filling vertical or horizontal recesses with an electrode material, e.g. polysilicon. In addition, in many cases, buried layers or thin films are formed in groove-like recesses between wires or recesses such as via holes or through-holes. If the film formation temperature is raised, films are preferentially grown at the entrances of these recesses. Consequently, the films will have a so-called overhanging shape, or the films will close the entrances of the recesses and voids will form in the recesses.
As stated above, in the conventional film forming method using the gas phase growth method, the high-rate film formation is not compatible with a good step coverage. In other words, in the conventional film forming method, it is difficult to form a film of a uniform thickness at a high rate or to form a void-free buried layer.